A conventional solid-state image pickup apparatus had a structure as shown in FIG. 6 in order to realize a slim and small apparatus. Legend 1 denotes a flexible printed circuit board (hereafter referred to as FPC) made with a film material such as polyimide. The FPC 1 is this figure is shown in a bent state. Legend 13 denotes a frame which holds an optical lens 6 and an optical filter 7. Legend 8 denotes a diaphragm section which takes in light from the outside. Legend 4 denotes a holding mount which holds the optical filter 7. This holding mount is fixed to the FPC 1. Legend 5 denotes a holding cap which holds the optical lens 6 and is disposed movably with respect to the holding mount 4 to obtain correct focus.
The holding mount 4 and the holding cap 5 are kept in a movable state to adjust position so that incident light from the diaphragm section 8 comes into focus on a solid-state image pickup device 9 through the optical filter 7. At the same time, an aperture 14 is provided in the FPC 1 to receive incident light from the optical lens 6. FIG. 6 shows a constitution where an IC component 10, such as a chip for image signal processing, is flip-chip bonded to the FPC 1 in the same manner as the case of the solid-state image pickup device 9. FIG. 6 also shows a constitution, as specific example, where chip components 12 such as resistors or capacitors are mounted on the FPC 1.
The operation of the solid-state image pickup apparatus will be explained below. The light coming in through the diaphragm 8 passes through the optical lens 6 and further passes through the optical filter 7. This light is then irradiated onto an image pickup area of the solid-state image pickup device 9 to form an image. Video information of the image is converted into electric signals in the solid-state image pickup device 9 and electrically transmitted to the FPC 1 via a flip-chip bonding pad section 11. The electric signals are further transmitted to the signal processing chip 10 and the lands provided on the FPC through the printed wiring of the FPC 1.
FIG. 7 shows an enlarged cross-section of the portion of the flip-chip bonding pad section 11 indicated by dashed lines in FIG. 6. A liquid adhesive with epoxy resin as its main component, which is referred to as underfill indicated by legend 31, is injected into the periphery of the flip-chip bonding pad section 11, and the underfill 31 is hardened to mechanically reinforce the electrical contact portion of the flip-chip bonding pad section 11, although this constitution is not shown in FIG. 6.
Thus, in the conventional solid-state image pickup apparatus, the flip-chip bonding pad sections 11 are provided for electrical contact between the solid-state image pickup device 9 and the FPC 1, and the underfill 31 is required for the periphery of the section.
This underfill 31 is injected into the periphery of the flip-chip bonding pad sections 11 in order to mechanically reinforce electrical contact portions between the flip-chip bonding pad section 11 and the land (contact edge) of the FPC 1, and the flip-chip bonding pad section 11 and the pad (contact edge) of the solid-state image pickup device 9. For the reinforcement, it is important that the underfill 31 is kept in contact with the FPC 1, the flip-chip bonding pad sections 11, and the solid-state image pickup device 9. Accordingly, the underfill 31 is originally a liquid with low viscosity, and a large amount of liquid is injected into the periphery. Since it is required to utilize this type of manufacturing process, an overflow of the underfill 31, which is referred to as bleed and indicated by legend 32, may occur.
On the other hand, the solid-state image pickup device 9 has an image pickup area 21 including photodiodes and transistors. Light reflected from a subject passes through the diaphragm 8, lens 6, and optical filter 7, further passes through a microlens 23 and a color filter 22 to form an image on the photodiodes corresponding to respective pixels forming the image pickup area 21.
When the underfill 31 covers the microlens 23 in the form of the bleed 32, the solvent of the underfill as the bleed 32 spreads over a large area, by a capillary phenomenon, along V-shaped grooves extending vertically and horizontally, like a checkerboard, which are specific to the area of the microlens 23 based on its form. Eventually, the bleed may reach the image pickup area 21. In such a case, the optical characteristics of the microlens 23 are disturbed because of the presence of the underfill 31. Resultantly, the light can not be focused on the photodiodes of the pixel area 21, which causes the image pickup sensitivity to be reduced.